Cloning and expression of a novel Na+-dependent neutral amino acid transporter structurally related to mammalian Na+/glutamate cotransporters

Saad Shafqat, Balaji K. Tamarappoo, Michael S. Kilberg, Ram S. Puranam, James O. McNamara, Ana Guadaño-Ferraz, Robert T. Fremeau

Research output: Contribution to journalArticlepeer-review

207 Citations (Scopus)

Abstract

A cDNA has been isolated from human hippocampus that appears to encode a novel Na+-dependent, Cl--independent, neutral amino acid transporter. The putative protein, designated SATT, is 529 amino acids long and exhibits significant amino acid sequence identity (39-44%) with mammalian L-glutamate transporters. Expression of SATT cDNA in HeLa cells induced stereospecific uptake of L-serine, L-alanine, and L-threonine that was not inhibited by excess (3 mM) 2-(methylamino)-isobutyric acid, a specific substrate for the System A amino acid transporter. SATT expression in HeLa cells did not induce the transport of radiolabeled L-cysteine, L-glutamate, or related dicarboxylates. Northern blot hybridization revealed high levels of SATT mRNA in human skeletal muscle, pancreas, and brain, intermediate levels in heart, and low levels in liver, placenta, lung, and kidney. SATT transport characteristics are similar to the Na+-dependent neutral amino acid transport activity designated System ASC, but important differences are noted. These include: 1) SATT's apparent low expression in ASC-containing tissues such as liver or placenta; 2) the lack of mutual inhibition between serine and cysteine; and 3) the lack of trans-stimulation. SATT may represent one of multiple activities that exhibit System ASC-like transport characteristics in diverse tissues and cell lines.

Original languageEnglish
Pages (from-to)15351-15355
Number of pages5
JournalJournal of Biological Chemistry
Volume268
Issue number21
Publication statusPublished - 25 Jul 1993
Externally publishedYes

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